Dynamo-electric machine



H. w. TAYLOR.

DYNAMO-ELECTRIC MACHINE. APPLICATION FILED AUG.27| 1919.

1,430,863.} Patented 0st. 3, 1922.

Inventor: Henry W. Tayl or, by W M H is Attorn ey.

Patented Oct. 3, 1922.

umrso STATES f COMPANY, A CORPORATION OF NEW YORK.

PATENT mm...

DYNAMOI-ELECQTRIC MACHINE.

llpplication filed August 27, 1919. Serial No. 320,152.

To all 'wjhomit may concern:

" Be it known that I, HENRY lVILLmM TAY- LoR,,a'subject of the King of Great Britain,- residing at Bilton in the county of VJar wickshire, England have invented certain new and. useful Improvements in Dynamd Electric lVlachines, of which the following is a specification." I

i The present invention relates to dynamo 10 electric. machines and more particularly to armature windings for alternating current machines.

In large alternating current generators in which. the windings disposed in the armatime slots, consist of conductors of consider able depth magnetic flux. across the slot "arising from the currentin the conductors, gives riseto a parasitic voltage withln the conductors which is liable to cause local cur- M rents; thereby producing heating of the conductors and the inefficient use oi the copper inlthe armature.

It has hitherto H current which will flow as aresult o lf these parasitic" voltages. first of all by. dividing the conductors into a number of separate multiple bars, and secondly by continuing this laminationot the complete conductor throughout the completecoil, and so con necting the ends thatvtheorder of thebars inthe conductors in the upper portion of the coil isithe reverseiofthe, order of the bars in the conductorsiin thelower portions oithecoih It is found, however, that on chines; with v erydeep conductors theloca1 currents-which flow even whenthe'se provisions are made, are still excessive and im- The magnetic flux which: passes across the bottom conductor in a slot depends only upon the'current being carried in this con- 1 duetor and therefore, increases, gradually:

fronrzero at the bottom of the conductor.

The flux in any other conductor nearer the mouth of the slot depends not "only upon the current which that conductor is carrying, but also upon the amount of current in the conductors below'the one in question.

The flu): across such conductor Imay, therefore, be considered as consisting of a variable element :duejto the current in that con-' 1; ductor and also'of a, constant element the proposed to limit the arge mapose limit'ations on the design of the mavalue of which depends upon the number of conductors below the conductor in ques tion; as for instance, the second conductor is subjected to the influence of one constant element of flux, the third conductor is subjected to the influence 01" two constant elements of flux, the lourth conductor to three constant elements of flux, and so on.

In the jointapplication or" myself. i le'th erick H. Clough, and Frank I Vxliitaher Elerial No. 3035101, filed June 10, 1919 there is described howin a two-layer multiple turn coil consisting oi conductors with a number of bars in multiple, these bars being" continuously insulated throughout the coil, the parasitic voltage arisingfrom the con stant elements of flux in the successive turns can becompletely or very nearly eliminated by suitably connecting the individual bars of the conductor at the .ends of the coil.

In the case of a coil in which the number of turns is divisible by two, it is possible to completely eliminate the parasitic voltage due to the constant flux elements in the manner proposed in the application referred to; but 'inthe case of a coilconsisting o1 a number of turns not divisible by'two the most perfect'arrangement in accordance with the disclosure in that application although a considerable improvement upon the previous method of constructing such coilsleaves the parasitic voltage due to a single constant flux element uneliminated.

I find, however, that if the coil is so constructed that the parasitic voltage due to this uneliminated single constant flux element is placed in opposition to the. parasitic voltage due to two variable flux elements, the parasitic voltage dueto thesingle consta'nt flux element then becomes completely eliminated.

VAccording to the present invention.theretore, in the construction of a multiple turn coil, I continuously insulate the separate bars of which the conductor throughout the coil, and so connect them in the successive half turns of the coil that the number of variable flux elements which remain unopposed is twice the number oi constant flux elements which are uneliminated, and the unopposed variable flux elements are in opposition to the uneliminated constant flux elements.

Theaccompanying drawing illustrates my consists invention. In it I have shown a three-turn coil arranged in two slots which contain the top and bottom portions of the same coil.

It will be understood that the two slots illustrated are not adj acent slots but occupy positions around the armature a full pole pitch apart or nearly a pole pitch apart according to whether the winding has a full or a fractional pitch.

The conductor is shown as being made up of live bars or laminz'itions designated by the numerals 1 to 5, while the half turns of the coil are marked a, a, 0, (Z, c and a being at the bottom of one slot while f is at the top or mouth of the other slot. It will. be seen that the bars in half turns a, Z), c and c are all arranged. in the same order, whereas those in (Z and 7' are in the reverse order.

in the arrangement shown, the constant flux element is the ilux, of uniform density, which threads the conductor comprising halt turn L, that is, which is confined between the top and bottom of this conductor, and is due entirely to the magnetomotive force below his conductor. The variable flux element is the flux, of a density increasing toward the mouth of the slot, which threads the conductor comprising halt turn Z) and is due solely to the current in conductor 5.

In order to set forth clearly and simply how the parasitic voltages are induced and the manner in which these voltages tend to cause current to How, let it be assumed for the moment that the laminations of the conductor comprising half turn Z) are connected in multiple at the ends of this half turn instead of being connected in multiple at the ends of the complete three-turn coil only. A given alternating current in the conductor comprising half turn a will cause an alternating flux to thread into and out of the conducting circuit or coil formed by laminations 1 and 5 which we have just assumed to be connected at their ends. This alternating flux induces an alternating electromotive force in the circuit comprising laminations l and 5 and this electromotive force is termed a parasitic voltage since it tends to circulate a local or useless current. Of course, there is a similar tendency to circulate current between laminations 2 and 4, and between other laminations, but it is believed that the explanation with reference to laminations 1 and 5 will be sufficient to enable the action to be fully understood. The flux threadingthe slot above half turn a, due to the current in a alone is uniformly distributed throughout the area of the slot and, therefore, the flux threading the conductor comprising half turn 7) and due to the current in adoes not vary from point to point from the bottom toward the top oi? the conductor but is at any given instantaneous value of the cur rent in half turn a constant for every point in the conductor comprising half turn I). This element of flux I have termed the constant flux element. Since there is but one half turn below half turn 6, the parasitic voltage in b is due to but one constant flux element. It is obvious that the parasitic voltage induced in 0 due to the half turns below 0 would be twice as great since this voltage would be caused by two equal constant flux elements due respectively to a and Z). lVith this explanation of the action of the constant flux element in producing a parasitic voltage, it is believed that, the action of the variable flux element in inducing a parasitic voltage will be obvious. Bean ing in mind that the laminations are not connected together at the end of each half turn but only at the end of the coil, it at once appears that the circulating currents which flow are due only to the resultant of the parasitic voltages induced in every half turn. of the complete coil.

It will be noted that there are four vari able flux elements, due respectively to half turns a, b, 0 and e which produce parasitic voltages in the same direction, while there are but two variable flux elements, due to half turns (Z and f respectively, which produce parasitic voltages in the opposite direction. There are, therefore, tWo unbalanced variable flux elements in favor of the first group of half turns. The constant flux elements in half turns a, b, c and e are equal to zero, one, two and four respectively, making a total of seven, while those in the second group d and f equal three and five respectively, making a total of eight, thus leaving a balance of one uneliminated constant flux element in the second group.

The single uneliminated constant element in the second group of half turns is therefore in opposition to the two unopposed variable elements in the first group of half turns and in this way the tendency for the uneliminated constant flux element to produce parasitic currents in the whole of the conductors of the coil is neutralized.

hen the winding has a fractional pitch the half turns of the upper portion of the coil are subjected to the external influence from the conductors in the bottom of the same slot which is not in phase with their own current. I find, however, that a considerable improvement is efl'ected in the elimination of eddy currents in this case as compared with the construction hitherto in use, although the improved construction does not entirely eliminate the constant flux element.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is

1. An armature winding comprising a conductor composed of a plurality 'of 1aminations insulated throughout the coil and connected in multiple at the ends of the the middle half turn of the top side of the ing similar and the opposite of the order of arrangement of the laminations in other half turns of the coil, the number of half turns in each group being chosen so as to balance as nearly as possible the parasitic voltages due to the constant flux elements in all of the half turns of the coil, the order of the laminations at the same time being chosen so that any unbalanced parasitic voltagedue to constant fiuX elements is opposed by the parasitic voltage due to double the number of variable flux-elements.

2. A two layer armaturewinding having three turns per coil, comprising a conductor composed of a plurality of laminations insulated throughout the coil and connected in multiple at the ends of the coil, the order of arrangement of the laminations" in the three half turns in the bottom side of the coil being the same and the same-as the order of arrangement of the laminations "in coil, the order of arrangement of the laminations in the remaining two half turns of the each coil being composed of a plurality of insulated laminations, characterized by the fact that thelaminations of the half turns are arranged in such a manner that the number of variable flux elements which remain unopposed is twice the number of constant flux elements which are uneliminated, the unopposed, variable flux; elements being in opposition to the uneliminated constant flux elements. y

In witness whereof, I have hereunto set my hand this eighth day of August, 1919.

HENRY WILLIAM TAYLOR. 

